1. Field of the Invention
The present invention relates to a color gamut mapping technology, and more particularly to a color gamut mapping method based on a color gamut of a source image.
2. Description of Related Art
The conventional color gamut mapping method is a mapping between a color gamut formed by connecting points corresponding to maximum saturation colors of three color components of red/green/blue (R/G/B) in a chromaticity space and a color gamut formed by connecting points corresponding to maximum saturation colors of other display base colors (such as three color components of cyan/magenta/yellow (C/M/Y) for a color printer) in a chromaticity space.
When performing a color gamut mapping, a source color gamut and a target color gamut should be considered. The source color gamut can be a color gamut of a source device or a color gamut of a source image. However, a color gamut mapping based on the color gamut of the source device has a greater loss than a color gamut mapping based on the color gamut of the source image in a transfer and reproduce process. Therefore, in the conventional art, a color gamut mapping between different devices is usually based on the color gamut of the source image in order to obtain a better mapping effect.
The conventional method for determining a color gamut of a source image includes following steps: respectively measuring stimulus matrixes (R(X, Y, Z), G(X, Y, Z), and B(X, Y, Z)) of grayscale of three primary colors of a source image; based on the color mixing principle, calculating and obtaining a stimulus matrix S(X, Y, Z) of grayscale of the source image through the stimulus matrixes R(X, Y, Z), G(X, Y, Z), and B(X, Y, Z); based on a conversion relationship between L*, a*, and b* in CIELAB chromaticity space and the stimulus matrix S(X, Y, Z) of grayscale of the source image, calculating and obtaining coordinate values L*, a*, and b* in the CIELAB chromaticity space of each pixel of the source image; based on the coordinate values L*, a*, and b*, determining the color gamut of the source image. Here, X represents red stimulus amount, Y represents green stimulus amount, Z represents blue stimulus amount, L* represents lightness index, and a* and b* represent chromaticity indexes.
However, the conventional method for determining a color gamut of a source image has to measure stimulus matrixes of grayscale of three primary colors of all pixel points. The method requires a long time, and the amount of calculation is large.